Examples for "Chain Actions" Node in Animation Nodes
Let say you have two actions, one of which is a Follow Spline Action with a duration of 50 frames, and the other is an action from an  empty's transform. Chaining both actions means combining them such that the second action starts after the first action ends, in this particular example, this means that the object will follow the spline for 50 frames, then the object will start following the empty. You can see this from the following example:



Notice that the object doesn't strictly follow the empty, that's because we enabled the Relative option. This option allows the second action to start from the location where the first action ended.